Errors while using animated fplot3

Hi, I want to do an animation of rotating 3d parametric curves. I tried with fplot3 and the first example of this page https://es.mathworks.com/help/matlab/ref/hgtransform.html. But I can only plot a graph at a time. My code is below, first plot is a helix and second one a circle, if use both i get this error

Error using matlab.graphics.function.ParameterizedFunctionLine/set Invalid or deleted object.

Error in untitled3 (line 17) set(h,'Parent',t)

¿What I am doing wrong?

ax = axes('XLim',[-1.5 1.5],'YLim',[-1.5 1.5],'ZLim',[-1.5 1.5]);
view(3)
grid on

[x,y,z] = cylinder([.2 0]);

xt = @(t) 0.75*sin(t);
yt = @(t) 0.75*cos(t);
zt = @(t) t;
ht = @(t) 0;

h(1) = fplot3(xt,yt,zt,[-pi pi]);
%h(2) = fplot3(ht,yt,xt,[-pi pi]);

t = hgtransform('Parent',ax);
set(h,'Parent',t)

Rz = eye(4);

for r = 0:.1:2*pi
    Rz = makehgtform('zrotate',r);

      set(t,'Matrix',Rz)

      pause(0.1);

      drawnow
  end

Answer 1

[Walter Roberson]

hold(ax, 'on')

After the axes call. It needs to be before the fplot3 call or else the fplot3 will erase the axes including getting rid of the grid and view